The overall aim of this project is to investigate the impact of eating breakfast through the School Breakfast Program (SBP) on childhood obesity. The SBP is a federal entitlement program that offers subsidized breakfast to low-income students who attend a school that participates in the program. A considerable body of research has examined the impact of eating breakfast through the SBP on nutrition outcomes; however, the conclusions from this research are generally limited due to methodological concerns. Using nationally representative data from the Early Childhood Longitudinal Study, Kindergarten Cohort (ECLS-K), and this project utilizes state mandates to account for the endogeneity of participation in the SBP. To increase participation in the SBP, many states mandated that schools must provide breakfast through the SBP if the percent of free and reduced-price eligible students exceeds a set threshold. These mandates present the opportunity to explore the impact of the SBP using a regression discontinuity design to compare students in schools where the number of free and reduced-price eligible students is just below the threshold and the school was not required to offer breakfast to students in schools where the number of free and reduced-price eligible students is just above the threshold and the school was required to offer breakfast. Through this research design, this project will improve upon the existing literature to determine the influence of the SBP on childhood obesity. Specifically, this research will (1) evaluate the impact of state mandates on whether schools participate in the SBP, (2) examine how schools implement the SBP in compliance with the state mandates, (3) evaluate the impact of the availability of the SBP in schools on BMI and childhood obesity, (4) evaluate the impact of state mandates on the participation of low-income children in the SBP, (5) evaluate the impact of eating breakfast through the SBP on BMI and childhood obesity, (6) examine differences in the impact of eating breakfast through the SBP by income and gender, and (7) examine whether the method of implementing the SBP in the school augments or diminishes the impact of the SBP. Overall, this project will identify whether the SBP and state mandates have had a causal effect on childhood obesity, how these state mandates are implemented and who benefits the most from the SBP and the state mandates requiring some schools to participate. The results from this project will serve to inform policymakers how the SBP and the expanded access to the SBP through state mandates may help in arresting or reversing the trend towards greater rates of childhood obesity.